1. Field of the Invention
The present invention relates generally to electrical connector, and more particularly to a connector having improved contacts arrangement.
2. Description of Related Art
Universal Serial Bus (USB) is a serial bus standard to the PC architecture with a focus on computer telephony interface, consumer and productivity applications. The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standard body incorporating leading companies from the computer and electronic industries. USB can connect peripherals such as mousse, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, external storage, networking components, etc. With more than 2 billion legacy wired (USB) connections in the world today, USB is the de facto standard in the personal computing industry.
As of 2006, the USB specification is at version 2.0 (with revisions). The USB 2.0 specification was released in April 2000 and was standardized by the USB-IF at the end of 2001. Previous notable releases of the specification were 0.9, 1.0, and 1.1. Equipment conforming to any version of the standard will also work with devices designed to any previous specification (known as: backward compatibility).
The USB 2.0 specification defines the following connectors: standard A plug and receptacle, standard B plug and receptacle, and mini-B plug and receptacle. Since USB has become a popular interface for exchanging data between cell phone and portable devices. Many of these devices have become so small it is impossible to use standard USB components as defined in the USB 2.0 specification. In addition the durability requirements of the cell phone and portable devices market exceed the specifications of the current interconnects. In addition, cell phone and portable devices have become so thin that the current mini-USB dose not fit well within the constraints of future designs. Additional requirements for a more rugged connector that still meet the USB 2.0 specification for mechanical and electrical performance was also a consideration. The mini-USB could not be modified and remain backward compatible to the existing connector as defined in the USG OTG specification. Since cell phone and other small portable devices are the largest market potential for USB, USB-IF published Micro-USB Cables and Connectors Specification to the USB 2.0 Specification, Revision 1.01 as of Apr. 4, 2007.
USB supports three data rates: 1) A Low Speed rate of up to 1.5 Mbit/s (187.5 KB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks; 2) A Full Speed rate of up to 12 Mbit/s (1.5 MB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed; 3) A Hi-Speed rate of up to 480 Mbit/s (60 MB/s). Though Hi-Speed devices are commonly referred to as “USB 2.0” and advertised as “up to 480 Mbit/s”, not all USB 2.0 devices are Hi-Speed. Hi-speed devices typically only operate at half of the full theoretical (60 MB/s) data throughput rate. Most hi-speed USB devices typically operate at much slower speeds, often about 3 MB/s overall, sometimes up to 10-20 MB/s. A data transmission rate at 20 MB/s is sufficient for some but not all applications. However, under a circumstance transmitting an audio or video file, which is always up to hundreds MB, even to 1 or 2 GB, currently transmission rate of USB is not sufficient. As a consequence, faster serial-bus interfaces are being introduced to address different requirements. PCI Express, at 2.5 GB/s, and SATA, at 1.5 GB/s and 3.0 GB/s, are two examples of high-speed serial bus interfaces.
From an electrical standpoint, the higher data transfer rates of the non-USB protocols discussed above are highly desirable for certain applications. However, these non-USB protocols are not used as broadly as USB protocols. Many portable devices are equipped with USB connectors other than these non-USB connectors. One important reason is that these non-USB connectors contain a greater number of signal pins than an existing USB connector and are physically larger as well. For example, while the PCI Express is useful for its higher possible data rates, a 26-pin connectors and wider card-like form factor limit the use of Express Cards. For another example, SATA uses two connectors, one 7-pin connector for signals and another 15-pin connector for power. Due to its clumsiness, SATA is more useful for internal storage expansion than for external peripherals. As discussed above, the existing USB connectors have a small size but low transmission rate, while other non-USB connectors (PCI Express, SATA, et al) have a high transmission rate but large size. Neither of them is desirable to implement modern high-speed, miniaturized electronic devices and peripherals.
To provide a kind of connector with a small size and a high transmission rate for portability and high data transmitting efficiency is much desirable. It has previously been proposed to extend the length of the plug and receptacle tongue portions of the existing USB standard-A connectors and to extend depth of the receiving cavity of the existing USB standard-A connectors, thereby to accommodate additional contacts in extended areas; or to provide the additional contacts on a reverse-side of the plug tongue portion and accordingly with regard to receptacle, to provide a lower tongue portion under a top receptacle tongue portion thereby four USB contacts are hold on the top tongue portion and additional contacts are accommodated on the lower tongue portion of the receptacle. To extending the length of the receptacle tongue portions of the existing USB standard-A connectors, it still hasn't an efficient proposal to assure the mating position when the existing USB plug inserted therein for backward compatibility. With contrast with existing USB standard-A receptacle, the receptacle with top and lower tongue portion is higher in height than existing USB receptacle. To achieve this object, at least eight contacts need to be added. Adding eight contacts in existing USB connector is not easy. As discussed above, the receptacle equipped with two tongue portions or plug and receptacle both with a longer length are also clumsiness. That is not very perfect from a portable and small size standpoint.
It has also previously been proposed to add additional five contacts to the existing mini-B USB receptacle. The original five contacts of mini-B receptacle are arranged on one side of the tongue and the additional contacts are arranged on the other side thereof. Therefore, the receptacle with additional contacts can receive an existing mini-B plug or another plug with five contacts for transmitting non-USB signals. When the plug for transmitting non-USB signals inserted into the receptacle, the five contacts thereof contact with the additional contacts of the receptacle, while the original contacts don't work. Although the receptacle is able to transmit both USB or non-USB signals, but the choice is selectively, the original and the additional contacts can't work simultaneously. Therefore, it is useless for increasing high-speed signal.
Hence, it is desired to provide an electrical connector to overcome the problems mentioned above.